Hemi pushrod clearance

Posted By: GregCon

Hemi pushrod clearance - 09/07/10 03:06 AM

How do you achieve pushrod clearance?

I needed to get some clearance on 3 of the 8 exhaust pushrods. These are Stage V heads. In the past I have always used die grinder with a long carbide burr. But it's time consuming, messy, and never that exact.

This time I tipped the head of my mill about 18 degrees on the Y axis and 3 degrees on the X axis and used a slightly undersized 5/8 end mill to egg shape the holes by about .055". I went ahead and did them all.

Time was 1 hour for the first head (including setup time) and 15 minutes for the second.

No more grinder for me!

Attached picture 6181773-IMG_2852.JPG

Posted By: Dragula

Re: Hemi pushrod clearance - 09/07/10 03:13 AM

I am surpirsed they weren't clearanced enough already. The problem I have seen is usualy the gaskets hit the push rods. I am not sure if its the Barton T&D rocker set-up or the gaskets, but I have now seen it twice with those rockers. Never seen the issue with the heads, but they were close.

Posted By: Performance Only

Re: Hemi pushrod clearance - 09/07/10 03:22 AM

Quote:

How do you achieve pushrod clearance?

we have several different mini boring bars that we use with the block and heads mocked up for 3/8 7/16 or 1/2" pushrods. we use a corresponding puck in the lifter bore that we can change the height on to match the lifter height that will be used in the build. these are all tools we made in house. after many years of doing it with the mill or die grinder we decided there was indeed a better way.

Posted By: GregCon

Re: Hemi pushrod clearance - 09/07/10 03:57 AM

That's good Dan, 'cause these are going on the block that you will soon be seeing!

I haven't assembled a Hemi yet that didn't need some sort of clearancing on the pushrods. I was actually pretty happy to see this engine needed only work on the three exhausts and no intakes.

Posted By: torkrules

Re: Hemi pushrod clearance - 09/07/10 12:31 PM

Quote:

How do you achieve pushrod clearance?

I needed to get some clearance on 3 of the 8 exhaust pushrods. These are Stage V heads. In the past I have always used die grinder with a long carbide burr. But it's time consuming, messy, and never that exact.

This time I tipped the head of my mill about 18 degrees on the Y axis and 3 degrees on the X axis and used a slightly undersized 5/8 end mill to egg shape the holes by about .055". I went ahead and did them all.

Time was 1 hour for the first head (including setup time) and 15 minutes for the second.

No more grinder for me!

Mine had tubes put in them since the ports break into the push rod area when ported, but they do have an added benefit of extra clearance.

I got some Cometic gaskets through FHO that have the push rod area either removed or pre-clearanced.

Posted By: an8sec70cuda

Re: Hemi pushrod clearance - 09/07/10 01:02 PM

I used a long shank bur bit on my die grinder. My block (KB) needed a bunch of clearancing. The heads and gaskets (MP and Cometic) fit fine.

Posted By: Chris_Holton

Re: Hemi pushrod clearance - 09/07/10 03:34 PM

I have a remer and add tubes, looks very clean...